1. Technical Field
The present invention relates generally to the field of pipe connections, and in particular, to a dual function, self restrained pressure gasket that is usable in a pipe connection.
2. Description of the Related Art
Pipes are commonly used for the conveyance of fluids under pressure, as in city water lines. They may also be used as free-flowing conduits running partly full, as in drains and sewers. Pipes for conveying water in appreciable quantities have been made of steel, cast iron, concrete, vitrified clay, and most recently, plastic including the various polyolefins and PVC.
It is well known in the art to extrude plastic pipes in an elongated cylindrical configuration of a desired diameter and to then cut the extruded product into individual lengths of convenient size suitable for handling, shipping and installing. Each length of pipe is enlarged or xe2x80x9cbelledxe2x80x9d at one end sufficiently to join the next adjacent pipe section by receiving in the belled end the unenlarged or xe2x80x9cspigotxe2x80x9d end of the adjacent length of pipe. The inside diameter of the bell is formed sufficiently large to receive the spigot end of the next section of pipe with sufficient clearance to allow the application of packing, caulking, elastomeric gaskets or other sealing devices designed to prevent leakage at pipe joints when a plurality of pipe lengths are joined to form a pipeline.
During a standard installation of a pipeline, in, for example, municipal installations, the joints between the pipe and the fitting must be restrained to accommodate varying pressures. There are various types of fitting connections which are commercially available and which are used in the waterworks industry. In one type of connection the current restraint mechanism is an external clamping device which is totally separated from the sealing function. Thus, a separate mechanism must perform the sealing function. In the other type of fitting connection, a gasket performs the sealing function. However, it is necessary that an external means must compress the gasket by mechanical action such as T-bolts. Each of these traditional restraining mechanisms adds considerable cost to the pipe installation as well as adding the possibility of human error depending on the specific conditions and applications.
Most current restraining systems offered in the industry require a substantial amount of labor to install. Under most installation conditions, the restraining systems are cumbersome to install and represent a substantial additional effort for the contractor. Also, current products typically require expensive and time-consuming corrosion protection efforts including special coatings, poly-wrapping, special wax tape or adding zinc anode nuts.
Accordingly, there is a need for a cost-effective, easy to manufacture and use mechanism for restraining pipe against internal forces at a pipe or fitting connection and join and seal at least two pipes to form a pipeline. The mechanism must be simple in design, economical to manufacture and dependable in operation.
It is therefore an object of the present invention to provide an improved self restrained pressure gasket which does not require assembly in the field and which thus simplifies installation.
Another object of the present invention is to provide an improved self restrained pressure gasket that is not subject to external corrosion.
Another object of the present invention is to provide an improved self restrained pressure gasket which is simple in design and dependable in operation.
In the method and apparatus of the invention, an improved self restrained pressure gasket is shown for restraining pipe against internal forces at a pipe or fitting connection and for joining and sealing at least two pipes to form a pipeline. The improved self restrained pressure gasket has the restraining mechanism as an integral part of the gasket thus simplifying field assembly. The preferred restraining mechanism is a stainless steel ring molded or incorporated into the gasket and inserted into a mating groove provided in a belled end opening of the mating female pipe section. The restraining mechanism has rows of teeth of varying length. When a pipe joint is assembled, the teeth engage at various points around the circumference of a mating male section of pipe. The various lengths of teeth adjust to the tolerances allowed in pipe manufacturing without losing gripping capacity. The gasket uses torsion to restrain the pipe and not set screws or wedges. By using torsion to restrain the pipe, point loading and pipe distortion or damage is reduced. Also, since the restraining mechanism is an integral or internal part of the gasket and manufactured of a corrosive resistant material, it is not subject to external corrosion.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.